EK 30 min exam, Lecture 7, Q. 156

[raab32]

A little confused about this question. So I understand that a free electron will experience the magnetic force as a centripetal force and will travel in a circular path. The magnetic force is pointing to the right, indicating a clockwise path for the e-. However, the E field is also pointing to the right, which means an electron would be drawn to the left (positive side) of the E field. My question is: why wouldn't the e- be affected by the E field? Why would it immediately move in a clockwise circular path as dictated by the B force? Thanks in advance!

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[soby10]

The direction of the electron is determined by the right hand rule as you stated. It moves clockwise for a negative charge.

Charged particles in B fields experience a force perpendicular to the field. ...(the E field is also pointing to the right). As far as the E field it is parallel. This is always true if it is to travel in a circular path. It cannot be in the same direction as the B field they are always perpendicular. In this case the B field is out of the page. So what they prob. mean is the E field is pointing parallel to direction of velocity.. and bc it's negative than it's antiparallel. But that doesn't only contribute to direction both B & E field as well as the charge and direction of velocity will according to RHR.